Clamp grips that are controlled purely mechanically between the release and the grip positions are known, for example, from EP 0 659 683 A. However, the cost of constructing the mechanical control is high.
From DE 297 13 510 U, mechanically controlled clamp grips are known, and also uncontrolled clamp grips which are then actuated by the containers themselves. The energy storage unit consists, for example, of a spiral or screw compression spring which is actively used between the grip arms. The uncontrolled clamp grip for bottles is opened by the bottles to be gripped and moved to the clamp grip over inclined feeding surface against the force of the energy storage unit, which acts in the direction towards the grip position, and brought into the grip position by the force of the energy storage unit. To remove the bottle, the latter is pulled out of the closed clamp grip, and, in the process, it swivels over the bevelled opening surfaces of the gripper arms against the force of the spring loaded energy storage unit. Due to the force of the spring storage device, the clamp grip automatically returns into the grip position. The mechanically controlled clamp grip is reset in the direction towards the force of the energy storage unit, for example, a rubber spring, which force acts in the direction towards the release position, by a rotatable control cam, into the grip position and back.
Container transport systems, particularly bottle transport systems, must satisfy stringent requirements with regard to microbiological conditions and cleaning; moreover, their operation must be reliable with long service lives and very fast work cycles. Physical springs, such as spiral springs or rubber springs or similar devices, which are positioned in the vicinity of the grip area, i.e., close to the containers to be gripped, are critical with a view to microbiology and cleaning, because small soiling particles become easily deposited there, and, moreover, they are frequently susceptible to aggressive cleaning media, which shorten the service life of the spring which can be damaged mechanically at any time, and break, with the result that the functional capacity of the clamp grip is impaired or lost (high risk of damage to the containers). In addition, during operation, abraded material or contents may separate from the spring.
In the bottle transport technology it has already been proposed to provide, in the case of controlled, multiple-compartment, articulated clamp grips, a retention mechanism with mutually attracting permanent magnets. Mutually attracting permanent magnets can be problematic because, if they come in contact with, or extremely close to, each other, an extremely strong force is required to loosen or separate them, which can lead to an undesired snapping movement of the clamp grip and to extremely high mechanical stress.